Chemical plant feed gas compression and conversion process system

Abstract

The invention relates to the technical field of chemical plant feed gas conversion, in particular to a chemical plant feed gas compression and conversion process system. In order to solve the problem of how to reduce heat sources except steam added from the outside of the system, the invention provides the chemical plant feed gas compression and transformation process system, and the last compression of feed gas is oil-free lubrication compression. Then performing conversion reaction through a degreasing agent furnace, a coal gas preheater I, a pre-conversion furnace, a quenching device I, a coal gas preheater II, a coal gas heat exchanger, a steam mixer, a quenching device II and a first conversion furnace to form converted gas, performing heat exchange on the converted gas through the coal gas heat exchanger, performing conversion reaction through a quenching device III, a second conversion furnace and a quenching device IV in sequence and then performing conversion reaction through a third conversion furnace; shift gas formed by the shift reaction of the third shift converter is divided into three paths, two paths respectively pass through a coal gas preheater I and a coal gas preheater II to exchange heat with raw material gas and then enter a quenching water heater, and the other path directly enters the quenching water heater. The process system disclosed by the invention is obvious in carbon reduction effect.

Description

Technical Field

[0001] The present invention relates to the technical field of raw material gas conversion in chemical plants, and specifically provides a raw material gas compression and conversion process system for chemical plants. Background Art

[0002] Most chemical plants use carbon-based fossil energy as raw materials, such as coal, oil, or natural gas. The raw material gas produced contains carbon monoxide, and carbon monoxide reacts with steam to produce hydrogen and carbon dioxide. In chemical plants using constant-pressure gas production, the raw material gas needs to be adiabatically compressed by a compressor, and then cooled to room temperature by circulating cooling water, separated from oil and water, and then sent to the conversion section.

[0003] The reaction of carbon monoxide with steam is an exothermic reaction, while the reaction with liquid water is an endothermic reaction. For energy conservation, the conversion section in industry generally adopts a segmented design, and the system heat balance is achieved by adding some external steam and inter-stage water spray evaporation.

[0004] The traditional raw material gas compression and conversion process after constant-pressure gas production is as follows: The raw material gas sent from the constant-pressure gas production section undergoes first-stage oil-lubricated compression, first-stage cooling, first-stage oil-water separation, second-stage oil-lubricated compression, second-stage cooling, second-stage oil-water separation, third-stage oil-lubricated compression, third-stage cooling, third-stage oil-water separation, fourth-stage oil-lubricated compression, fourth-stage cooling, fourth-stage oil-water separation, and then passes through two-stage oil removal in a wire mesh oil removal furnace and an oil remover furnace. Subsequently, it passes through a gas preheater, a steam mixer, and a gas heat exchanger to absorb the reaction heat and raise the temperature of the raw material gas to the catalyst reaction temperature. After multi-stage conversion reaction and heat absorption, the converted gas exchanges heat with the raw material gas deoiled by the oil remover furnace through the gas preheater to cool down. Then, the converted gas passes through a boiler feed water preheater and a demineralized water preheater to recover its remaining heat, and finally is cooled to room temperature by a circulating water cooler and sent out of the conversion section. The raw material gas heated by the gas preheater returns to the conversion system.

[0005] The traditional raw material gas compression and conversion process after constant-pressure gas production already has a high utilization efficiency of the conversion reaction heat, and the heat lacking in the system can be achieved by adding a certain amount of steam outside the system. Under the background of "dual carbon" in recent years, the comprehensive energy consumption limit per unit product of synthetic ammonia has been further reduced. Reducing the heat source other than steam added from outside the system is an effective method for the conversion process to reduce the amount of externally added steam, save energy, reduce emissions, and lower the energy consumption of synthetic ammonia. However, how to reduce the heat source other than steam added from outside the system while ensuring the normal operation of the conversion process system has become a difficult problem that people need to solve currently. Summary of the Invention

[0006] In order to solve the problem of reducing the heat source other than steam added from outside the system while ensuring the normal operation of the raw material gas conversion process system, the present invention provides a new raw material gas compression and conversion process system for chemical plants.

[0007] The present invention is realized by adopting the following technical solutions: A process system for compressing and converting raw material gas in a chemical plant. The raw material gas sequentially undergoes first-stage oil-lubricated compression, first-stage cooling, first-stage oil-water separation, second-stage oil-lubricated compression, second-stage cooling, second-stage oil-water separation, third-stage oil-lubricated compression, third-stage cooling, third-stage oil-water separation, fourth-stage oil-free lubricated compression, an oil remover furnace, a gas preheater I, a pre-conversion furnace, a quench cooler I, a gas preheater II, a gas heat exchanger, a steam mixer, a quench cooler II, and then undergoes a conversion reaction in a first conversion furnace to form converted gas. The converted gas formed by the conversion reaction in the first conversion furnace is then heat-exchanged with the raw material gas preheated by the gas preheater II in the gas heat exchanger, and then sequentially passes through a quench cooler III, a second conversion furnace, and a quench cooler IV, and then undergoes a conversion reaction in a third conversion furnace to form converted gas. The converted gas formed by the conversion reaction in the third conversion furnace is divided into three paths. Two paths respectively enter a quench water heater after heat-exchanging with the raw material gas through the gas preheater I and the gas preheater II, and the other path directly enters the quench water heater. After heating, the quench water is sent to the quench cooler I, the quench cooler II, the quench cooler III, and the quench cooler IV. The converted gas after passing through the quench water heater then sequentially passes through a boiler feed water preheater, a condensate separator I, a demineralized water preheater, a condensate separator II, a circulating water cooler, and a condensate separator III and then is sent out of the conversion section.

[0008] Principle description: 1) The last stage of the raw material gas compression is changed to oil-free lubricated compression, reducing the consumption of lubricating oil in the raw material gas compressor and the oil content carried by the raw material gas. Therefore, the last-stage circulating water cooling and separation can be cancelled, reducing the circulating water consumption of the compressor and the investment in cooling equipment; 2) In the traditional process, the heat generated by the compression of the raw material gas is taken away by the cooling circulating water, wasting its heat. In this process, after the raw material gas is adiabatically compressed, the high-temperature gas directly enters the conversion system, bringing the adiabatic compression heat into the conversion system, reducing the external heating amount of the conversion system and realizing the saving of steam consumption; 3) By setting a pre-conversion furnace, it is convenient to remove harmful substances such as oxygen in the raw material gas and protect the catalyst from being damaged by poisons; 4) By setting a pre-conversion furnace, the oxygen in the raw material gas can be removed, avoiding dew point corrosion caused by the coexistence of water and oxygen, and avoiding sulfuric acid corrosion caused by the coexistence of hydrogen sulfide, water, and oxygen; 5) Reasonably setting quench cooling and inter-stage heat exchange improves the heat utilization efficiency and reduces the amount of additional steam.

[0009] Furthermore, the condensate separated by the condensate separator I is sent to the quench water heater again through a quench water pump, so that the condensate separated by the condensate separator I is recycled and reused.

[0010] Further, a pre-reformer side is also provided with a pre-reformer bypass circuit, and a pre-reformer bypass valve is arranged on the pre-reformer bypass circuit. When the protective agent in the pre-reformer is deactivated, the pre-reformer is cut off, the pre-reformer bypass valve is opened, and the pre-reformer bypass circuit is connected, so that the pre-reformer can be separately isolated for replacement, avoiding the contact between the catalyst and air when replacing the protective agent.

[0011] Further, the oil remover furnace includes two serially connected oil remover furnaces I and II. The oil remover furnace I and the oil remover furnace II are respectively bypassed with an oil removal bypass circuit I and an oil removal bypass circuit II. The oil removal bypass circuit I is provided with a bypass valve I, and the oil removal bypass circuit II is provided with a bypass valve II. When the oil remover furnace I or the oil remover furnace II reaches the service life for replacement, they can be switched with each other through the bypass valves for online replacement treatment, or the two oil remover furnaces can be used together to reduce the poisoning of the catalyst by the oil-contaminated raw material gas.

[0012] The beneficial effects produced by the present invention are as follows: The process system described in the present invention effectively utilizes the heat of raw material gas compression to reduce the heat source other than steam added from outside the system, with obvious carbon reduction effect, effectively reducing the energy consumption of synthetic ammonia, improving economic benefits, and being ingeniously designed to effectively recycle heat. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The drawings here are incorporated into the specification and form a part of this specification, showing the embodiments in line with the present invention, and are used together with the specification to explain the principles of the present invention.

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0015] Figure 1 It is a schematic diagram of a traditional raw material gas compression and conversion process system; Figure 2 It is a schematic diagram of the raw material gas compression and conversion process system described in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] In order to more clearly understand the above-mentioned objects, features, and advantages of the present invention, the following will further describe the solutions of the present invention. It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0017] In the description, it should be noted that the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance. It should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", and "joined" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0018] In the following description, many specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only a part of the embodiments of the present invention, rather than all the embodiments.

[0019] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0020] Taking the process system transformation of a certain company as an example for illustration.

[0021] Embodiment 1: Adopt the traditional raw material gas compression and conversion process system.

[0022] The carbon monoxide content in the raw material gas generated by the fixed-bed normal-pressure gas production is about 27%. The raw material gas is adiabatically compressed to a pressure of 3.5 MPa(A) through a four-stage piston compressor, cooled to the normal temperature of 40°C to separate oil and water, and the heat of raw material gas compression is taken away by the cooling circulating water and discharged into the atmosphere. The conversion section adopts the all-low-temperature conversion process. Before the raw material gas is sent into the conversion, it passes through two stages of oil removal, namely the wire mesh oil removal furnace and the oil removal agent furnace, and then exchanges heat with the converted gas after the reaction in the fourth conversion furnace through the gas preheater to raise the temperature to above 140°C. The heated raw material gas then passes through the steam mixer and the gas heat exchanger to absorb the reaction heat to raise the temperature of the raw material gas to the catalyst reaction temperature of 260°C and enters the first conversion furnace for reaction. The temperature after the reaction is about 360°C, and it is cooled to about 260°C by spraying water for humidification in the first quenching cooler and enters the second conversion furnace for reaction. The temperature of the gas after the reaction is about 330°C, and it is cooled to 270°C after exchanging heat with the raw material gas through the gas heat exchanger, and then cooled to about 210°C by spraying water for humidification in the second quenching cooler and enters the third conversion furnace for reaction. The temperature of the gas after the reaction is about 275°C, and it is cooled to about 200°C by spraying water for humidification in the third quenching cooler and enters the fourth conversion furnace for reaction. The temperature of the gas after the reaction is about 215°C. After exchanging heat through the gas preheater, the temperature of the converted gas is about below 140°C, and then the heat of the converted gas is recovered through the boiler feed water and the demineralized water preheater and the temperature is reduced to about 60°C, and finally it is cooled to the normal temperature of 40°C by the circulating water cooler and sent out of the conversion section.

[0023] Embodiment 2: The raw material gas compression and conversion process system described in the present invention The specific process system is that the raw material gas sequentially passes through first-stage oil-lubricated compression, first-stage cooling, first-stage oil-water separation, second-stage oil-lubricated compression, second-stage cooling, second-stage oil-water separation, third-stage oil-lubricated compression, third-stage cooling, third-stage oil-water separation, fourth-stage oil-free lubricated compression, oil remover furnace 1, oil remover furnace 2, gas preheater 1, pre-reformer, quench cooler 1, gas preheater 2, gas heat exchanger, steam mixer, quench cooler 2, and then forms reformed gas through the reforming reaction in the first reformer. The reformed gas formed through the reforming reaction in the first reformer is then heat-exchanged with the raw material gas preheated by gas preheater 2 in the gas heat exchanger, and then sequentially passes through quench cooler 3, the second reformer, quench cooler 4, and then forms reformed gas through the reforming reaction in the third reformer. The reformed gas formed through the reforming reaction in the third reformer is divided into three paths. Two paths respectively enter the quench water heater after heat-exchanging with the raw material gas through gas preheater 1 and gas preheater 2, and the other path directly enters the quench water heater. After heating, the quench water is sent to quench cooler 1, quench cooler 2, quench cooler 3, and quench cooler 4. The reformed gas after passing through the quench water heater then sequentially passes through the boiler feed water preheater, condensate separator 1, demineralized water preheater, condensate separator 2, circulating water cooler, and condensate separator 3 and then is sent out of the reforming section.

[0024] When this process is specifically implemented, the carbon monoxide content in the raw material gas generated by the compressed air is about 27%. The raw material gas is adiabatically compressed to a pressure of 3.5 MPa(A) by a four-stage piston compressor. The last-stage oil-lubricated compression uses oil-free lubricated compression, canceling the lubricating oil and water cooler. The temperature of the compressed gas is about 140°C and is directly sent to the reforming system without cooling. That is, it first passes through gas preheater 1 to absorb the reforming reaction heat of the third reformer to raise the temperature of the raw material gas to the reaction temperature of the pre-reformer catalyst, about 215°C, enters the pre-reformer to remove harmful substances such as oxygen in the raw material gas. The temperature of the reacted gas is about 245°C, and is cooled to about 150°C by spraying water for humidification in quench cooler 1. It sequentially passes through gas preheater 2 and gas heat exchanger to raise the gas temperature to about 315°C, and then is mixed with high-pressure steam in the steam mixer, and is cooled to about 200°C by spraying water for humidification in quench cooler 2 and enters the first reformer for reaction. The temperature of the reacted gas is about 350°C, and then is cooled to 270°C in the gas heat exchanger, and is cooled to about 200°C by spraying water for humidification in quench cooler 3 and enters the second reformer for reaction. The temperature of the reacted gas is about 255°C, and is cooled to about 200°C by spraying water for humidification in quench cooler 4 and enters the third reformer for reforming reaction. The temperature of the reacted gas is about 217°C and is divided into three streams. Two of them are mixed after passing through gas preheater 1 and gas preheater 2 respectively, and the third stream enters the quench water heater to heat the quench water in stages to fully recover the heat above 140°C and return it to the reforming system. The heat of the reformed gas below 140°C after heat-exchanging with the quench water is recovered by the boiler feed water and demineralized water preheater and the temperature is reduced to about 60°C, and finally is cooled to room temperature of 40°C by the circulating water cooler and sent out of the reforming section.

[0025] In specific implementation, the condensed water separated by the first condensed water separator is sent to the quenching water heater through the quenching water pump, so that the condensed water separated by the first condensed water separator is recycled and reused.

[0026] In specific implementation, a pre-reformer side bypass loop is also provided on the pre-reformer side. A pre-reformer side bypass valve is provided on the pre-reformer side bypass loop. When the protective agent in the pre-reformer is deactivated, the pre-reformer is cut off, the pre-reformer side bypass valve is opened, and the pre-reformer side bypass loop is connected, so that the pre-reformer can be separately isolated for replacement, avoiding contact between the catalyst and air when replacing the protective agent.

[0027] In specific implementation, the oil remover furnace includes two serially connected oil remover furnaces, namely the first oil remover furnace and the second oil remover furnace. An oil removal bypass loop one and an oil removal bypass loop two are respectively bypassed on the first oil remover furnace and the second oil remover furnace. A bypass valve one is provided on the oil removal bypass loop one, and a bypass valve two is provided on the oil removal bypass loop two. When the first oil remover furnace or the second oil remover furnace reaches the end of its service life and needs to be replaced, they can be switched with each other through the bypass valves for on-line replacement treatment, or the two oil remover furnaces can be used together to reduce the poisoning of the catalyst by the oil in the raw material gas.

[0028] Effect comparison: For a synthetic ammonia enterprise with an annual output of 220,000 tons, the raw material gas volume is 95,000 Nm3 / h, and the carbon monoxide content in the converted gas leaving the system is about 1.2%. According to the equilibrium constant and equilibrium temperature difference of a certain catalyst of the same brand, the additional steam required in the conversion system of the traditional process is about 13 t / h, and the quenching water is about 22.5 t / h. After adopting the process technology of the present invention, the additional steam required in the conversion system is about 6.5 t / h, and the quenching water is about 26.5 t / h. Compared with the original process, the additional steam is saved by about 6.5 t / h.

[0029] Calculated according to 8000 hours / year: Only saving steam can achieve energy saving of about 1.029 million GJ, equivalent to about 3511.85 tons of standard coal.

[0030] Calculated at 150 yuan / t for the price of high-pressure steam, the steam cost can be reduced by about 7.8 million yuan per year.

[0031] The circulating water can be reduced by 300 t / h. Calculated at 0.1 yuan / t for the price, the circulating water cost can be reduced by about 240,000 yuan per year.

[0032] Without considering the equipment investment of the water cooler and separator and the lubricating oil cost, and without considering the extension of the catalyst life and the equipment protection life, only steam and circulating water can reduce the cost by about 8.04 million yuan per year.

[0033] It can be clearly seen through comparison that the process of the present invention has obvious energy-saving and carbon-reducing effects and good economic benefits.

[0034] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Although the foregoing embodiments have been described in detail, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered by the protection scope of the claims.

Claims

1. A process system for compressing and converting raw material gas in a chemical plant, characterized in that, The raw gas sequentially passes through first-stage oil-lubricated compression, first-stage cooling, first-stage oil-water separation, second-stage oil-lubricated compression, second-stage cooling, second-stage oil-water separation, third-stage oil-lubricated compression, third-stage cooling, third-stage oil-water separation, fourth-stage oil-free lubricated compression, oil remover furnace, gas preheater 1, pre-reformer, quench cooler 1, gas preheater 2, gas heat exchanger, steam mixer, quench cooler 2, and then undergoes a conversion reaction in the first converter to form converted gas. After the converted gas formed by the conversion reaction in the first converter exchanges heat with the raw gas preheated by gas preheater 2 in the gas heat exchanger, it then sequentially passes through quench cooler 3, the second converter, quench cooler 4, and then undergoes a conversion reaction in the third converter to form converted gas. The converted gas formed by the conversion reaction in the third converter is divided into three paths. Two paths respectively enter the quench water heater after exchanging heat with the raw gas through gas preheater 1 and gas preheater 2, and the other path directly enters the quench water heater. After heating, the quench water is sent to quench cooler 1, quench cooler 2, quench cooler 3, and quench cooler 4. The converted gas after passing through the quench water heater then sequentially passes through the boiler feed water preheater, condensate separator 1, demineralized water preheater, condensate separator 2, circulating water cooler, and condensate separator 3, and then is sent out of the conversion section.

2. The chemical plant raw material gas compression and conversion process system according to claim 1, characterized in that, The condensate separated by condensate separator 1 is sent back to the quench water heater by the quench water pump.

3. A raw material gas compression and conversion process system for a chemical plant according to claim 2, characterized in that, A pre-reformer bypass loop is also provided on the side of the pre-reformer, and a pre-reformer bypass valve is provided on the pre-reformer bypass loop.

4. A raw material gas compression and conversion process system for a chemical plant according to claim 3, characterized in that, The oil remover furnace includes two oil remover furnaces 1 and 2 connected in series. Oil remover furnace 1 and oil remover furnace 2 are respectively bypassed by oil removal bypass loop 1 and oil removal bypass loop 2. A bypass valve 1 is provided on oil removal bypass loop 1, and a bypass valve 2 is provided on oil removal bypass loop 2.

Images